* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
.contents {
  width: 1200px;
  height: 200px;
  border: 1px solid rgba(0, 0, 0, 0.3);
  margin: 0 auto;
  margin-top: 50px !important;
}
#left {
  width: 200px;
  height: 100%;
  list-style: none;
  float: left;
}
#left li {
  width: 100%;
  height: 50px;
  background-color: #ffffff;
  color: black;
  text-align: center;
  line-height: 50px;
}
.active {
  background-color: #42a5f5 !important;
  color: #ffffff !important;
}
#right {
  width: 998px;
  height: 100%;
  background-color: yellow;
  float: left;
  padding: 20px;
}
